The vascular tree is a complex network of vessels designed to maintain, at its outermost subdivisions, a surface area between blood and tissues for the exchange of gases and nutrients and for the drainage of waste products. During the early stages of inflammation, the sensitive mechanisms relating to microvascular perfusion are altered so that vascular integrity is compromised, blood contents leak into tissues, and hemostasis may develop. In the whole organism, severe and abrupt injury to the microcirculation distorts tissue architecture, impedes delivery of oxygen to cells, and causes extensive fluid loss from the vascular compartment, leading to edema, electrolyte imbalance, shock, and other circulatory disorders. The search for and identification of agents that modulate the immediate responses of inflammation may generate drugs with clinical benefit.
Recent studies suggest that certain peptides act as agonists to inhibit inflammation, defined by Cotran et al. (Robbins: Pathologic Basis of Disease, (4th ed., 1989), Ed. Robbins, 2:39-86, Philadelphia: Saunders) as the reaction of vascularized living tissue to local injury. Specific antagonists, by design, work one-on-one against substances that promote inflammation, and the efficacy of a single antagonist may be limited if more than one mediator is released during tissue injury. An agonist, a term introduced by Reuse (Br. J. Pharmacol., 3, pp. 129-62 (1948)) to describe a chemical that activates biological events, would be more efficacious than an antagonist if it could suppress convergent processes initiated by more than one inflammatory mediator. The concept of drugs as anti-inflammatory agonists was discussed by Svensjo and Persson in 1985 (Handbook of Inflammation, Ed. Bonta, 5:51-82, Amsterdam: Elsevier).
For example, we have recently described one set of relatively small, CRF-related peptides (Wei and Thomas, Annu. Rev. Pharmacol. Toxicol., 33, pp. 91-108 (1993)) and one of us has described another, related set of small CRF-related peptides (Wei, U.S. Pat. No. 5,177,060, issued Jan. 5, 1993, of common assignment herewith) for uses as anti-inflammatory agents. Thus, crude peptides corresponding to the 11-residue carboxyl terminus of human/rat CRF were found to have anti-inflammatory activity. Further characterization of the structures within the crude peptide mixture revealed that substitution of the glutamic acid residue (E) with an anisolylated glutamic acid derivative increased overall anti-inflammatory potency. The anisole derivative was apparently a by-product of the temperature-dependent Friedel-Crafts acylation reaction that occurs during hydrogen fluoride cleavage of glutamyl-containing peptides. Several peptides containing the anisolylated glutamic acid derivative were made with D-amino acid substitutions (denoted by the lower case of the single letter code). Pending U.S. patent application Ser. No. 07/925,081, filed Aug. 4, 1992, inventors Wei and Thomas, of common assignment herewith, also describes the anti-inflammatory uses of CRF-related peptides.
The search for additional compounds useful in anti-inflammatory applications continues. One of us had earlier attempted to determine if particular dynorphin compounds might merit possible development for anti-inflammatory uses. In 1986, Wei et al., J. Pharmacol. Exp. Therap., 238, pp. 783-787 (1986), studied dynorphin A (1-13) and dynorphin A (1-10) amide in "neurogenic inflammation," a pathophysiological condition in which antidromic stimulation of the sensory nerve increased plasma protein leakage from small blood vessels. The potencies of dynorphin A (1-13) and dynorphin A (1-10) amide in the test system for neurogenic inflammation, measured as the median effective dose (ED.sub.50) producing 50% inhibition of dye leakage, relative to saline-injected controls, were not high: 1.9 (1.5-2.4) mg/kg and 5.0 (3.5-7.2) mg/kg injected by the intravenous route, respectively, and thus they were not in the range of potency which merited possible development for clinical applications.
Dynorphin A (1-13) was subsequently reported to prevent edema in the anesthetized rat's paw after thermal injury at doses of 3.75 mg/kg administered intravenously (Wei and Kiang, European J. of Pharmacology, 168, pp. 81-86 (1989). These studies led to the conclusion that dynorphin A (1-13) lacked potency in reducing inflammation in injury models.
The endogenous opioid peptides can be divided into three distinct families (endorphins, enkephalins, and dynorphins), all contain one of two, five amino acid sequences at their amino-terminus and are present in different neuronal pathways within the central and peripheral nervous system. Molecular genetics studies have shown that these three families of opioid peptides are derived from three distinct precursors. Proopiomelanocortin (POMC) gives rise to the endorphins, as well as to adrenocorticotropic hormone (ACTH) and to the melanotropic hormones (MSH's). [Met] enkephalin, [Leu] enkephalin and a related heptapeptide and octapeptide are derived from proenkephalin. The third family is derived from prodynorphin, and includes dynorphin A, dynorphin B (also known as rimorphin) and alpha- and beta-neoendorphin.
A variety of uses for dynorphin and dynorphin-related compounds have been known for applications pertaining to combinations with narcotic analgesics or with respect to opiate activity. In addition, a compound related to the dynorphin A (1-13) compound, but without the N-terminal tyrosine and glycine (sometimes referred to as dynorphin A (3-13)), has been of recent research interest. Additional peptide fragments have been studied, such as reported by Takemori et al. in their JPET abstract of 1993 reporting dynorphin A (2-17) as suppressing naloxone-induced withdrawal and the expression of morphine tolerance in morphine dependent mice, and similar suppressive activity for dynorphin A (2-14), (2-11), and (2-8).
U.S. Pat. No. 4,361,553, issued Nov. 30, 1982, inventors Loh and Lee, sets out the sequence of the first thirteen peptides for the naturally occurring dynorphin A (containing seventeen amino acids), which had been discovered to have potent agonist properties in guinea pig ileum and mouse vas deferens. This patent describes the discovery that dynorphin, and particularly dynorphin A (1-13) has an effect in hosts tolerant to narcotic analgesic opposite to the effect which has been observed in naive animals (an inhibition of morphine or .beta.-endorphin-induced analgesia). Thus, dynorphin A (1-13) potentiates the analgesic effect in tolerant hosts. Dynorphin was found useful in conjunction with a narcotic analgesic in order to reduce the amount of narcotic analgesic administered per dose.
U.S. Pat. No. 4,396,606, issued Aug. 2, 1983, inventor Goldstein, describes isolation of dynorphin A (1-13) which has a structure beginning at the N-terminus with tyrosine. This compound was found to be substantially more active than the enkephalins and .beta.-endorphin in a guinea pig ileum test, and compositions containing the compound were suggested to be analgesic.
U.S. Pat. No. 4,462,941, issued Jul. 31, 1984, inventors Lee et al., describes dynorphin amide analogs with the first seven amino acids as in dynorphin A (1-17) and 1-13, but with the next several amino acids as AA.sup.8l -AA.sup.9 -AA.sup.10 wherein AA.sup.8 is isoleucine, leucin, or lysine, AA.sup.9 is arginine or proline, AA.sup.10 is proline, and a carbonyl carbon at the AA.sup.10 terminus is amidated. In tolerant animals, on the other hand, the dynorphin A (1-10) amide analogs appears to be a more potent and selective analog than dynorphin A (1-13).
U.S. Pat. No. 4,481,191, issued Nov. 6, 1984, inventors Wei et al., describes a method for treating high blood pressure and disturbances of cardiac function by administrating dynorphin-related opioid peptides. It appears that endogenous opioid peptides condition the sensitivity of the peripheral nerves to stimuli that affect heart rate and blood pressure.
U.S. Pat. No. 4,684,624, issued Aug. 4, 1987, inventors Hosobuchi et al., describes the use of certain dynorphin-related peptides in the acid or amidated form, to treat patients suffering from cerebral ischemia. The administration of these opioid peptides to patients suffering from acute focal cerebral ischemia has been found useful in prolonging survival, and appears useful in partially reversing neurologic deficits resulting from cerebral ischemia.